MASc Oral Exam

MASc Oral Exam | Engineered-Polysaccharide Reinforced Hybrid Composites for Automotive Applications, by Dinesha Ganesarajan

Linda Sherwood — Tue, 10 Dec 2019 15:25:22 +0000

MASc Oral Exam | Engineered-Polysaccharide Reinforced Hybrid Composites for Automotive Applications, by Dinesha Ganesarajan Linda Sherwood Tue, 12/10/2019 - 10:25

You are welcome to attend Dinesha Ganesarajan's MASc oral exam, where they will discuss their research into engineered-polysaccharide reinforced hybrid composites for automotive applications.

MASc Oral Exam | Functionalized Vanadium Oxide as the Cathode Material for Rechargeable Aqueous Zinc-ion Batteries, by Mei Han

Linda Sherwood — Wed, 27 Nov 2019 18:42:29 +0000

MASc Oral Exam | Functionalized Vanadium Oxide as the Cathode Material for Rechargeable Aqueous Zinc-ion Batteries, by Mei Han Linda Sherwood Wed, 11/27/2019 - 13:42

You are invited to attend Mei Han's MASc oral exam, where they will discuss their research into strategies to improve the electrochemical performance of vanadium-based electrodes in rechargeable aqueous zinc-ion batteries.

Abstract

The battery offers a viable solution for storing intermittent energy supplies associated with renewable energy production. Although lithium-ion batteries take up the most battery market, they are still limited by lithium metal resources, high cost and safety concerns. With this regard, aqueous batteries with mildly acidic electrolytes hold a promise for large-scale energy storage. In particular, zinc, as an attractive alternative to lithium metal, has been employed in aqueous rechargeable batteries due to its low-cost, high safety and environmental friendliness. Layered vanadium oxide (V2O5) as cathode material has gained enhanced interests in the studies of rechargeable aqueous zinc-ion batteries (RAZBs) due to its relatively high capacity.

However, commercial V2O5 shows poor stability during cycling since the zinc ion intercalation causes degradation of the cathode and battery components.

Therefore, in this project, two strategies involving surface coating and metal-ion doping are proposed and utilized to improve the electrochemical performance of vanadium-based electrodes in RAZBs.

First, we introduce a coating method to fabricate polymer-modified cathode materials for aqueous zinc-ion batteries, which display improved electrochemical performances under both ambient and elevated temperature conditions. A polymer-coated cathode is demonstrated and the assembled battery delivers a high capacity of 195.7 mAh·g-1 (at a current density of 1 A·g-1), with only 9.5% capacity decay at room temperature after 200 cycles. Even at an elevated temperature (60°C), the polymer-coated battery still shows outstanding capacity retention, of 80% vs. 25% for bare V2O5 cathode after 150 cycles.

Second, two kinds of metal ions (Zn2+ and Na+) are doped simultaneously into the V2O5 interlayer by a molar ratio of Zn:Na = 2:1 to form a metal-ion doped cathode material Zn0.38Na0.19V2O5 (ZNVO). Besides, in order to prevent the extraction of Na ions from the positive electrode, an additional 2M sodium salt is added to the 2M ZnSO4 aqueous solution to prepare a dual-ion electrolyte. This dual-ion system (containing dual ion-doped positive electrode and dual ion electrolyte) offers a long-term cycle life, ~ 89% capacity retention after 4000 cycles, and a relatively high discharge capacity of 190 mAh·g-1 at 1 A·g-1 during fast charge / discharge process.

More importantly, this dual-ion electrolyte effectively suppresses zinc dendrite formation on the anode surface because of the electrostatic shield mechanism, where creating a positively charged shield around the sharp zinc protuberances. Thus, this dual-ion system provides the excellent electrochemical performance of Zn // ZNVO batteries and holds a promise for realizing practical applications of zinc-ion batteries.

Supervisor: Professor P Chen

MASc Oral Exam | A Novel Back-Off Algorithm for the Integration Between Dynamic Optimization and Scheduling of Batch Processes Under Uncertainty, by Yael Izamal Valdez Navarro

Linda Sherwood — Tue, 12 Nov 2019 18:26:52 +0000

MASc Oral Exam | A Novel Back-Off Algorithm for the Integration Between Dynamic Optimization and Scheduling of Batch Processes Under Uncertainty, by Yael Izamal Valdez Navarro Linda Sherwood Tue, 11/12/2019 - 13:26

You are invited to attend Yael Izamal Valdez Navarro's MASc oral exam, where they will present a decomposition algorithm for obtaining robust scheduling and control decisions. It iteratively solves scheduling and dynamic optimization problems while approximating stochastic uncertainty through back-off terms, calculated through dynamic simulations of the process.

Supervisor: Professor Luis Ricardez Sandoval

MASc Oral Exam | Cobalt Decorated Hierarchical Porous Carbon Spheres for High Sulfur Loading Lithium Sulfur Batteries, by Ruohan Jiang

Linda Sherwood — Mon, 26 Aug 2019 20:19:36 +0000

MASc Oral Exam | Cobalt Decorated Hierarchical Porous Carbon Spheres for High Sulfur Loading Lithium Sulfur Batteries, by Ruohan Jiang Linda Sherwood Mon, 08/26/2019 - 16:19

In this closed MASc oral exam, Ruohan Jiang will present their research into the use of cobalt decorated hierarchical carbon sphere (CZ/HPC) to overcome the obstacles associated with lithium sulfur battery technology.

Abstract

With the growing need of energy storage devices, the market shows a strong requirement of lithium-based batteries. Nowadays, Lithium ion batteries (LIBs) are dominating the battery field because of its high energy density and low safety risks. However, the energy density of LIB is pushed to its principle limitation. To further improve the battery performance, another new battery mechanism has been developed. Lithium sulfur batteries (LSB) have four times higher energy density of LIBs in principle. LSB are considered as the next generation of batteries in electric vehicles and portable devices by many scientists and material engineers.

In another hand, there are still a lot of obstacles on lithium sulfur technology. Firstly, sulfur is an insulator, so it must be mixed with other conductive supporters to form the electrode which decrease the energy density respect to total weight. During the oxidation-reduction reaction, soluble polysulfide is generated as an intermediate. It is soluble in electrolyte and diffuse through the separator toward the cathode and react with lithium. In the charging process, the Li₂S on the cathode cannot be reduced which is a waste of the active material. The Li₂S layer form on anode also deactivated the lithium plate and cause the capacity fading.

In this project, cobalt decorated hierarchical carbon sphere (CZ/HPC) is designed to overcome these obstacles. This spherical material has three types porous structure including 3 nm mesopores, 150 nm middle-size macropores and large carbon bubbles which is around 2 μm. Spherical structure can provide good ion transfer and high conductivity at the same time. Large carbon bubbles and middle-size macropores provide high sulfur loading in the electrode and the mesoporous structure increase the utility of the sulfur which reflect to high specific capacity. The size of the particle is around 3.5 μm, and larger size of particle made it easier to form thick electrode.

The sulfur loading of the battery is over 10 mg/cm² and the weight percentage of the active material in the cathode is 72.3% which provide excellent energy density of the battery. To limit the shuttle effect, cobalt nanoparticles generated by calcination of ZIF-67 particles, as an effective polysulfide absorption material, is synthesized on the carbon sphere. Spray dry, which is widely used in the industry, is chosen to synthesize CZ/HPC, and the price of the precursor is relatively cheap that gives CZ/HPC a potential of commercialize.

Supervisor: Dr. Zhongwei Chen

MASc Oral Exam | Real Impact of CO2 Utilization: A Dynamic LCA Approach, by Majd Tabbara

Linda Sherwood — Mon, 26 Aug 2019 18:56:08 +0000

MASc Oral Exam | Real Impact of CO2 Utilization: A Dynamic LCA Approach, by Majd Tabbara Linda Sherwood Mon, 08/26/2019 - 14:56

You are invited to attend Majd Tabbara's MASc oral exam, where they will discuss their research into the environmental costs and benefits associated with the conversion of already-captured CO₂ into final chemicals or energy products.

Abstract

Global warming has received widespread attention in recent years due to increasing levels of carbon dioxide (CO₂) and other pertinent greenhouse gases in the atmosphere. Various solutions have been proposed to reduce the net CO₂ emissions, including switching to renewable energy and CO₂ capture and sequestration. A probable and attractive alternative to CO₂ storage could be CO₂ utilization, which is defined as the conversion of already-captured CO₂ into final chemicals or energy products. Customarily, a static life cycle analysis (LCA) has been employed to comprehend the environmental costs and benefits associated with CO₂ utilization processes. Essentially, the LCA procedure retains a crucial aspect in understanding the extent to which CO₂ is truly being mitigated within a CO₂ utilization process. However, the scope and extent of the LCA procedure requires careful attention. Although ultimately all of the CO₂ utilized will likely end up in the atmosphere, a comprehensive dynamic LCA needs to be conducted in order to encompass a time scale to represent the time that CO₂ is being displaced by within a proposed CO2 utilization process.

The research presented within this thesis primarily focused on assessing two products, methanol (MeOH) and dimethyl carbonate (DMC), through the application of the dynamic LCA procedure. Initially, a model schematic, inclusive to the necessary equations, was established so as to compute the net CO₂ emissions within a given system. This included the use of a 620 MW natural gas combined cycle power plant, that accounted for de-rating, to produce the required amount of CO₂ necessary for the utilization process.

Additionally, the conventional process and the so-called CO₂ utilization process for manufacturing MeOH, were developed and simulated in Aspen Plus^TM.

Normalizing the values to 1 (tonne MeoH/hr), the cumulative amount of CO₂ emitted within both the conventional and utilization processes is 1.878 (tonne CO2/hr) and 1.703 (tonne CO2/hr) respectively. These results were then utilized so as to compute the net CO₂ emissions within each respective approach. Subsequently, the values attained were then used as an input to the dynamic LCA framework yielding in the necessary environmental results. After an in-depth comparison, the utilization approach proved superior, from an environmental perspective, when contrasted against the conventional route of manufacturing MeOH. This is seen as the cumulative impact on radiative forcing, at year 100, was computed for both routes yielding in 4.328*10^-5

(W/m^2) for the conventional approach and 3.613*10^-5 (W/m^2) for the utilization approach. Notably, implementing the utilization approach would result in a 16.51 % percent reduction in the cumulative impact of radiative forcing at year 100. Furthermore, a sensitivity analysis was also conducted on the utilization route and this showed that an increase in the CO₂ storage duration within the MeOH product results in a diminished environmental impact.

Similarly, an environmental comparison-based assessment was conducted to analyze both a conventional and CO₂ utilization approach of manufacturing DMC. The conventional approach analyzed the partial carbonylation route, whilst the utilization approach assessed the urea route through reactive distillation. Subsequent to the cradle-to-grave computations, the obtained CO₂ emissions within both approaches were further inputted into the dynamic LCA framework. Overall, the cumulative impact on radiative forcing, at year 100, was calculated for both routes resulting in 5.118*10^-5 (W/m^2) for the conventional approach and 5.859*10^-5 (W/m^2) for the utilization approach.

From an environmental standpoint, employing this utilization approach to manufacture DMC results in a 14.46 % increase in the cumulative impact of radiative forcing at year 100. A sensitivity analysis was also performed to study the effect of increasing the CO2 storage duration, in the DMC product, on the cumulative impact on radiative forcing. An inverse relationship was observed showing that an increase in the CO₂ storage duration yields a relative decrease in the cumulative impact on radiative forcing.

Supervisors: Professors Peter Douglas and Eric Croiset

MASc Oral Exam | Self-assembled Metal Organic Framework Microflowers as Polysulfides Immobilizers for Lithium Sulfur Batteries, by Xiaoyuan Dou

Linda Sherwood — Wed, 14 Aug 2019 17:37:43 +0000

MASc Oral Exam | Self-assembled Metal Organic Framework Microflowers as Polysulfides Immobilizers for Lithium Sulfur Batteries, by Xiaoyuan Dou Linda Sherwood Wed, 08/14/2019 - 13:37

Xiaoyuan Dou will discuss their research on self-assembled metal organic framework microflowers as polysulfides immobilizers for lithium sulfur batteries during their closed MASc oral exam.

Abstract

A unique flower-like metal organic framework (ZnHMT) is synthesized by a facile and efficient method. The obtained ZnHMT microflowers were employed for the construction of a multifunctional interlayer towards improved Li-S batteries.

Supervisor: Professor Zhongwei Chen

MASc Oral Exam | Cobalt-Hexamine (HMT) Metal-Organic Framework-derived Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions, by Yue Niu

Linda Sherwood — Wed, 14 Aug 2019 17:33:10 +0000

MASc Oral Exam | Cobalt-Hexamine (HMT) Metal-Organic Framework-derived Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions, by Yue Niu Linda Sherwood Wed, 08/14/2019 - 13:33

You are welcome to attend Yue Niu's MASc oral exam, in which they will discuss their research of Cobalt-hexamine (HMT) metal-organic framework-derived bifunctional electrocatalyst for oxygen reduction and evolution reactions, which promises implmentation advantages for rechargeable Zinc-air batteries.

Abstract

With the high requirement of increasing people’s living standards and building a more sustainable society, electrochemical energy storage devices with large energy density, high power density, and long term durability are greatly needed to mitigate the consumption of fossil fuels. Among all those well-known energy storage systems, zinc-air batteries are one of the most appealing candidates due to sufficient and inexpensive resources applied, promising energy density, as well as the high reduction potential of zinc.

However, Zn-air batteries always suffer from relatively high overpotential, which is predominantly originated from the sluggish kinetics of oxygen electrocatalytic reactions. Enormous efforts have been devoted to the development of active bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).

Although noble-metal catalysts, such as platinum, iridium, and their alloys have been proved to own outstanding electrochemical performances for oxygen electrocatalysis, their insufficient catalytic bifunctionality, rarity and high cost hinder the commercial utilization. As a result, the design and synthesis of cost-effective, robust and highly stable bifunctional electrocatalysts to replace noble metal catalysts for zinc-air batteries are greatly desirable to realize the commercialization of Zn-air batteries. In recent years, the metal-organic frameworks (MOFs) are burgeoning as attractive precursors for the fabrication of transition-metal-based bifunctional oxygen electrocatalysts with controllable nanostructures due to the structural and compositional advantages of the MOF.

Herein, a layered Co-hexamine coordination framework is prepared and used as an efficient precursor to synthesize high-performance ORR/OER bifunctional electrocatalyst featured with cobalt oxide and cobalt phosphide heterostructured structure (denoted as CoO/CoxP). This design not only generates a high surface area to expose more active sites but also guarantees the excellent bifunctionality by integrating the cobalt phosphide and cobalt oxide, which are specifically active to OER and ORR, respectively. Moreover, the synergistic effects of these nanoparticles, as well as the superior structural features, can further boost the catalytic activities. As a result, CoO/CoxP outperforms the state-of-art non-noble metal catalysts and the noble metal benchmark with a half-wave potential of 0.86 V for ORR and a low potential of 1.60 V to generate a current density of 10 mA cm-2 for OER. The promising bifunctional catalytic activity thus makes it highly promising to be implemented in rechargeable Zinc-air battery.

Supervisor: Professor Zhongwei Chen

MASc Oral Exam | Factors Affecting Virucidal Properties of a Nickel-Brass Alloy, by Sadru Walji

Linda Sherwood — Tue, 06 Aug 2019 18:20:27 +0000

MASc Oral Exam | Factors Affecting Virucidal Properties of a Nickel-Brass Alloy, by Sadru Walji Linda Sherwood Tue, 08/06/2019 - 14:20

Sadru Walji will discuss his research on the virucidal properties of a copper-nickel-zinc alloy designed to replace stainless steel high-touch surfaces.

Abstract

Copper and its alloys have contact biocidal properties, and seek to aid cleaning of high-touch surfaces. However, virucidal properties of these surfaces is poorly understood.

The goal of this thesis is to assess the virucidal properties of a copper-nickel-zinc alloy designed to replace stainless steel high-touch surfaces, investigate factors that may diminish the virucidal properties, evaluate virucidal activity of each alloy component, and characterize leaching of metals from the alloy.

MASc Oral Exam | Reverse Water Gas Shift Reaction over High Surface Area γ-Al2O3 Supported Mo2C Synthesized by Reverse Microemulsion Method, by Guanjie Sun

Linda Sherwood — Wed, 24 Jul 2019 20:18:40 +0000

MASc Oral Exam | Reverse Water Gas Shift Reaction over High Surface Area γ-Al2O3 Supported Mo2C Synthesized by Reverse Microemulsion Method, by Guanjie Sun Linda Sherwood Wed, 07/24/2019 - 16:18

Guanjie Sun will discuss their research related to using greenhouse gases to produce renewable synthetic fuels and chemicals in a closed MASc oral exam.

Abstract

Increasing concentrations of greenhouse gases (GHG), especially carbon dioxide (CO₂), in the atmosphere are forecasted to result in adverse environmental impacts. One attractive approach for mitigation of CO₂ emissions is utilizing this gas for the production of renewable synthetic fuels and chemicals. In particular, the reverse water gas shift (RWGS) reaction converts CO₂ to CO, which can further be used to generate valuable chemicals.

In this study, MoOx and o2C nanoparticles were synthesized by the reverse microemulsion method and analyzed their performance as RWGS catalysts. The catalyst composition, morphology and crystalline structure were investigated by inductively coupled plasma – optical emission spectrometry (ICP-OES), Brunauer Emmett-Teller (BET) method, X-ray diffraction (XRD), temperature programmed reduction (TPR), transmission electron microscope (TEM) and scanning electron microscope (SEM).

The impact of using different preparation methods (e.g. reverse microemulsion versus impregnation method) on the catalytic activity, selectivity and stability were determined using a fixed bed reactor experimental setup. The thermal decomposition processes of the spent catalysts were investigated using thermogravimetric analysis-Fourier Transform Infrared spectroscopy (TGA/FTIR).

Overall findings have indicated that Mo2C nanoparticles prepared by the reverse microemulsion method showed higher conversion, 100% selectivity to CO, and significantly more stable performance over extended times on stream than the commercial catalyst, Cu/ZnO/Al2O3 for the RWGS reaction.

Supervisors: Professors David Simakov and Luis Ricardez Sandoval

MASc Oral Exam | CO2 Methanation Over Alumina-Supported Cobalt Oxide and Carbide Synthesized by Reverse Microemulsion Method, by Yue Yu

Linda Sherwood — Wed, 24 Jul 2019 20:07:07 +0000

MASc Oral Exam | CO2 Methanation Over Alumina-Supported Cobalt Oxide and Carbide Synthesized by Reverse Microemulsion Method, by Yue Yu Linda Sherwood Wed, 07/24/2019 - 16:07

Yue Yu will discuss their research of CO₂ methanation over alumina-supported cobalt oxide and carbide synthesized by reverse microemulsion method in a closed MASc oral exam.

Abstract

In the past age, CO₂ conversion catalysts have gained attention due to various environmental issues caused by CO₂ emission. Catalytic reduction of CO₂ using renewable hydrogen as reductant to produce renewable fuels is considered as a potential solution to store the surplus renewable energy and reduce the CO₂ emission. Alumina-supported cobalt oxide and cobalt carbide catalysts prepared by reverse microemulsion (RME) method were investigated for CO₂ methanation. Results showed that the prepared catalysts were nanosized particles ranged from 5-15 nm. XRD, BET, SEM and TEM were used for catalysts characterization and TPR was conducted to study the reducibility.

The catalytic performance of these catalysts was studied by CO₂ methanation reaction. At 400 °C, 3 bar, under a 60,000 mL gcat-1 h-1 flow (H2:CO2=4:1), the selectivity to methane on alumina-supported cobalt carbide catalysts can reach 0.96 and the conversion of CO₂ was 0.78, showing high catalytic activity and mild reaction condition. With increasing pressure, the conversion of CO₂, as well as the selectivity to CH₄ both increased and reached 0.91 and 0.98 respectively at 11 bar showing excellent performance towards CO₂ methanation.

In-situ FTIR was used to study the mechanism of the reaction on alumina-supported cobalt oxide catalysts. The pathway from CO₂ to methane and adsorbed intermediates on catalysts were investigated. Intermediates and adsorbed species on the catalysts were investigated during the reaction. At lower temperature and lower gas concentration, CO₂ was physically adsorbed on the surface as carbonates. When the reaction condition was achieved, adsorbed CO₂ started to be reacted to CO and CH₄ and intermediate species started to appear.

Supervisors: Professors David Simakov and Aiping Yu